A compressor for a gas turbine engine includes at least one rotor disc having an array of rotor blades mounted thereon. Until relatively recently, it was common practice to produce rotor blades with integral platforms, the platforms forming the inner wall of the rotor annulus in use. The blade and platform were manufactured as a single unit from a common material. This had the disadvantage that the platforms were formed from a relatively heavy material. Further, any damage to the platform often necessitated the replacement of the entire blade.
Recent developments have led to the use of separate annulus fillers, as an alternative to blade platforms. The annulus fillers are located between adjacent rotor blades and generally have their own features for removably locating them on the rotor disc rim. Such fillers may be manufactured from relatively lightweight materials and, in the event of damage, may be replaced independently of the rotor blades.